1. Field of the Invention
The present invention relates to a sun tracking device for use in a solar power generation system, in a solar power collection system, or in other solar power utilization systems; and more specifically relates to a su tracking device which can provide a high sun light collecting efficiency by tracking the direction of the sun, which of course changes with time.
2. Description of the Prior Art
For some considerable time now, attention has been paid to solar power generation, which makes use of inexhaustible and free energy source in place of diminishing energy sources such as oil. However, in such solar power generation systems, because the cost of silicon as the material for solar cells is so high and the energy conversion efficiency thereof is so low, in the order of 10% to 15%, that the time required for recovering the cost of construction of such a power generation system may extend a number of years, this fact prevented a successful commercialization of such solar power generation.
Therefore, with the aim of improving the efficiency of solar energy conversion, various research and development efforts have been spent in placing Fresnel lenses and other sun light collecting devices in front of a solar cell array, and designing hybrid systems which utilize both sun light and sun heat; but even in such systems substantial improvement is sun light collecting efficiency cannot be achieved without providing a sun tracking device which can rotate the solar cell array in the direction of sun light from sun rise to sun set.
As such a tracking device, there exists a prior art type device in which: a multitude of solar cell arrays are arranged on a rotatable table which can rotate in a horizontal plane; a plurality of light sensors (photodiodes and so on) set at different angles with respect to the direction of rotation of the rotatable table are mounted on the rotatable table; and the deviation between the light receiving plane of the solar cell arrays and the sun light is detected from the difference in the light receiving amounts between the light sensors; so that the sun light may be tracked by rotating the turntable following the changes in the direction of sun light. This type of system is disclosed in Japanese Patent Laid Open Publication No. 58-193510, among other sources.
However, in such prior arts, support members for the solar cell arrays, as well as a large number of solar cell arrays, are mounted on the rotatable table, and the rotatable table itself has to have a certain strength for supporting them, and therefore the weight load on the rotatable table and upon the support means therefor becomes extremely great, thereby requiring a large drive energy for driving the rotatable table and preventing satisfactory improvements in the energy conversion efficiency which can justify the increase in the cost of construction.
Furthermore, according to such prior arts, since the weight burden on the rotatable table is great, the design thereof requires the support base for rotatably supporting the rotatable table to be sufficiently strong and the frictional resistances arising from the rotation of the rotatable table to be as small as possible, and such disadvantages as complexity of the structure, bulkiness of the overall structure, and increase in the construction cost inevitably ensue.